Muffler



Jan. 2, 1940. z wlLMAN 2,185,489

MUFFLER Filed July 18, 1955 MIVENTOIR ZYGMUNT WILMAN ATTORNEY PatentedJan. 2, 1940 PATENT OFFICE MUFFLER Zygmunt Wilman, Courbevoie, Seine,France Application July 18. 1935. Serial No. 32,023

In France July 19, 1934 v 1 Claim.

The present invention has for its object an improved system of mufflersfor internal combus-- tion engines or the like.

The muiller according to the invention is based upon the principle ofthe damping of the sound waves which are produced by the noise of theexplosion of the engines and are propagated in the exhaust pipe of suchengines, and for this purpose, it comprises a. single chamber of special0 construction, or in the case of more improved apparatus, a smallnumber of such chambers, each of which serves for the damping of acertaln number of sound waves.

The present muiller avoids all obstruction of the exhaust of the gas,due to the fact that it comprises an open conduit employed for thecirculation of this gas. surround the said conduit, and they communicatewith the latter through orifices whose disposition corresponds to theacoustic characteristics of the sound waves propagated in the exhaustconduit, and whose object is to provide for the transmission of thesound waves into the corresponding chambers of resonance and of damping.

The muffler according to the invention may be constructed by mountinghelical chambers of varying section around the exhaust conduit. Each ofthese chambers consists of a helix of varying pitch which is wound uponthe exhaust conduit and with which the said chambers are p aced inacoustic communication.

A single damping chamber can be constructed by the use of a sheet metalpiece which is wound in spiral form around the exhaust conduit. Due toits appropriate form, the said conduit divides the spiral chamber ofthis construction into a certain number of spaces which communicate withthe exhaust conduit through orifices so arranged as to transmit, to thesaid chambers, the sound waves which are to be dampened.

The damping chamber may have any suitable form, but it is so arrangedthat each point will possess different acoustic properties, and thedamping chamber, as a whole, has a range of acoustic properties which isextensive and con- .tinuous, corresponding to the different wavelengths.

In order to attenuate the principal wave due to the Operating of theengine, the invention provides for the use of acoustic interference, bythe utilization of exhaust tubes whose length is adjustable at will,according to the speed of the engine.

The accompanying drawing shows various embodiments of the invention.

Fig. 1 shows a muiller comprising helical chambers surrounding theexhaust conduit.

Figs. 2 and 3 show a modification of the arrangement of the helicalchambers of Fig. 1.

The damping chambers As shown in Fig. 1, the muiller of the simplestconstruction comprises an exhaust conduit l, upon which is wound a helix2. The whole device is inclosed in a casing 3. The exhaust gascirculates in the direction of the arrows. It is observed that the helix2 has a variable pitch, and that it thus forms a continuous series ofhelical chambers of variable capacity. orifices 4 in the conduit Iconnect this latter with helical chambers 5.- The length of the mufiler,as well as the length of the intake tubes 6 and the offtake tubes 1 forthe gas, and also the arrangement of the orifices 4 and theirdimensions, are chosen in such way as to correspond to the acousticcharacteristics of the sound waves propagated in the conduit I. Theorifices 4, especially, must be located at the nodal points of twosuccessive uneven harmonics. As will be noted, the number of suchorifices increases when proceeding to the ends of the muilier, and thepitch of the helix decreases.

In order to damp the principal wave, the pipes 6 and I may have anadjustable length in order to obtain an optimum of silence for a givenengine speed, which is the general operating speed.

As shown in Fig. 2, a modified form of the muffler disclosed in Fig. 1has another perforated tube 9 which is also surrounded by a helix ofvariable pitch. This device may be considered as a complete mufller, inthe case in which the partial damping of the noise is considered assuificient. However if it is desired to obtain a complete damping of thenoise, it will be necessary to mount a certain number of like devices inseries.

The mufller shown in Fig. 3 relates to one of the combinations of thetwo devices shown in Fig. 2. The inner tubes 9 correspond to theharmonics of high frequency, and the sections of the tube l, to theharmonics of low frequency.

I claim:

Improvement in muiiiers for motors comprising an open end exhaust tubecapable of being connected to the exhaust of said motor, a helix ofgraduated pitch wound around said exhaust tube, said exhaust tube havingorifices formed therein, a second tube having said exhaust tube andhelix mounted therein forming a continuous helical chamber of graduatedcapacity between said first and second tubes for dampening the harmonicsof high frequency, orifices formed in said second tube, a helix ofgraduated pitch wound around said second tube and a resonant casinghaving said second tube and helix mounted therein forming a continuoushelical chamber of graduated capacity between said second tube and saidcasing for dampening the harmonics of low frequency and also having saidfirst tube passing therethrough.

ZYGMUNT WILMAN.

